Илья Лебедев

class CreateJoinTableTeamUser < ActiveRecord::Migration[5.0]
  def change
    create_join_table :teams, :users do |t|
      t.index [:team_id, :user_id]
      t.index [:user_id, :team_id]
    end
  end
end

class CreateTeamUser < ActiveRecord::Migration[5.0]
  def change
    create_table :team_users do |t|
      t.integer team_id
      t.integer user_id
    end
  end
end

rails g migration CreateTeamUsers team_id:integer user_id:integer